High-Efficiency Bidirectional Buck-Boost Converter for Photovoltaic and Energy Storage Systems in a Smart Grid

This paper proposes a new bidirectional buck-boost converter, which is a key component in a photovoltaic and energy storage system (ESS). Conventional bidirectional buck-boost converters for ESSs operate in discontinuous conduction mode (DCM) to achieve zero-voltage switching turn-ON for switches. However, operation in DCM causes high ripples in the output voltage and current, as well as low power-conversion efficiency. To improve the performance of the conventional converter, the proposed converter has a new combined structure of a cascaded buck-boost converter and an auxiliary capacitor. The combined structure of the proposed converter reduces the output current ripple by providing a current path and the efficiency is increased. A prototype was built and tested to verify the effectiveness of the converter. The proposed converter has a maximum efficiency of 98%, less than 5.14 Vp. p of output voltage ripple, and less than 7.12 Ap. p of output current ripple. These results were obtained at an input voltage of 160 V, switching frequency of 45 kHz, output voltage of 80-320 V, and output power of 16-160W. The experimental results show that the proposed converter has improved performance compared to the conventional converter.